The alignment of liquid crystal phases in cells can be brought about in various ways and is usually effected by rubbing a glass plate coated with a polymer layer or by the inclined vapour deposition of a SiO.sub.x layer on a glass plate. Generally uniformly aligned layers are produced in this manner.
It is, however, also possible to obtain a structured orientation of the liquid crystal phase. This can be achieved, for example, by coating a glass plate with a polymer with which are admixed, for example, photochemically orientatable dyestuff molecules or photochemically dimerizable molecules, as described, for example, in EP-A-0445629. These methods are, however, not optimal, since on the one hand the solubility of such orientatable molecules in the polymer is limited and on the other hand the stability with time can not be guaranteed to a sufficient extent. A further possibility for the production of photochemically orientatable polymer layers is described, for example, in Jpn. J. Appl. Phys. Vol. 31 (1992), 2155 and comprises esterifying the free hydroxy groups on the polymer with dimerizable units. A disadvantage of this method is, however, the fact that the esterification of the free hydroxy groups on the polymer with photochemically dimerizable units usually leads to a non-reproducible and, above all, to an incomplete conversion. The free hydroxy groups still present in the orientating layer lead to an undesired ion solubility.
There is therefore a need to find an orientating layer which no longer has the aforementioned disadvantages.